Hi,
The orders in pos are treated differently from sale orders in Odoo. You can see that the pos orders are in model pos.order and orders in the sales module are in sale.order. 
You either can customise or can refer the app-store that satisfy this requirement.

If you are using version 15, you can check out this free module.https://apps.odoo.com/apps/modules/15.0/sale_order_pos/

Hope it helps

Hi,

Why you need to see the pos orders in the sale order ? If you are looking for reporting purpose the sales report will also show the sales details from point of sale and sales.

Sales -> Reporting -> Sales Analysis

Thanks

Hi,

It's not a default feature in odoo, instead if you need the same you customize or use any third-party addons.

please check this module by OCA,

https://apps.odoo.com/apps/modules/16.0/pos_order_to_sale_order/

Thanks