Hi,

We can easily achieve this by the following code,
First, we need to inherit a field in settings or any place you want,

from odoo import fields, models


class ResConfigSettings(models.TransientModel):
    """Inherited the model to add the fields"""
    _inherit = 'res.config.settings'

    sale_purchase_synchronization = fields.Boolean(string='Synchronization',
                                                   config_parameter='inter_company_synchronization.
sale_purchase_synchronization',
                                                   help='Boolean field is use '
                                                        'to enable the inter '
                                                        'company sale and '
                                                        'purchase '
                                                        'synchronization')

Then the next step we need to super the confirm button in both sales and purchases.

from odoo import models


class PurchaseOrder(models.Model):
    """Inherited this model to create corresponding SO while creating PO"""
    _inherit = 'purchase.order'

    def button_confirm(self):
        """Super the button confirm function to create SO to the
        corresponding company when confirming the PO."""
        res = super(PurchaseOrder, self).button_confirm()
        res_config_settings = self.env['res.config.settings'].search([])
        company_id = self.env['res.company'].search(
            [('name', '=', self.partner_id.name)])
        transit_locations = self.env['stock.location'].search(
            [('active', '=', True), ('usage', '=', 'transit')])
        if transit_locations and res_config_settings and \
                res_config_settings[-1].sale_purchase_synchronization:
            self.env['sale.order'].sudo().create({
                'partner_id': self.env.company.partner_id.id,
                'company_id': company_id.id,
                'client_order_ref': self.name,
                'order_line': [(0, 0, {
                    'product_id': rec.product_id.id,
                    'product_uom_qty': rec.product_qty,
                    'price_unit': rec.price_unit,
                    'tax_id': rec.taxes_id,
                    'price_subtotal': rec.price_subtotal
                }) for rec in self.order_line],
            })
        return res

from odoo import models


class SaleOrder(models.Model):
    """Inherit to create PO while create SO"""
    _inherit = 'sale.order'

    def action_confirm(self):
        """Super the function to create PO to the corresponding company
           when confirming the SO"""
        res = super(SaleOrder, self).action_confirm()
        res_config_settings = self.env['res.config.settings'].search([])
        company_id = self.env['res.company'].search(
            [('name', '=', self.partner_id.name)])
        transit_locations = self.env['stock.location'].search(
            [('active', '=', True), ('usage', '=', 'transit')])
        if transit_locations and res_config_settings and \
                res_config_settings[-1].sale_purchase_synchronization:
            self.env['purchase.order'].create({
                'partner_id': self.env.company.id,
                'company_id': company_id.id,
                'origin': self.name,
                'order_line': [(0, 0, {
                    'product_id': record.product_id.id,
                    'product_qty': record.product_uom_qty,
                    'price_unit': record.price_unit,
                    'price_subtotal': record.price_subtotal,
                }) for record in self.order_line],
            })
        return res

Hope it helps