i was value create or write sale.order to stock.picking but now done

this code.

def action_confirm(self):

    res = super(SaleTransportOrder,self).action_confirm()

    for rec in self:

   rec.picking_ids.write({'transport_id':rec.transport_id.id})

   return res

this is answer

sale_id field already exists in stock.picking so you need to add "sale_stock" to your depends in __manifest__.py file and then you can add related field as below to get  transport_id  in stock.picking.

You don't need to override  action_confirm  in sale order. so you can remove it. 

class SaleTransportOrder(models.Model):
    _inherit = 'sale.order'

transport_id = fields.Many2one('transport.management', string="Transport Via", required=True)
    
class Stockpicking(models.Model):
    _inherit = "stock.picking"

transport_id = fields.Many2one(related="sale_id.transport_id ", string="Transport Via", store=True)