Microsoft Dynamics 365
We need to enable the PO and Purchase Request from Point of sale
For now you can receive POs created from D365 in POS.
Usually by business restrictions, stores cannot create POs by themselves - this is D365 process, because you need to select the best matching vendor, control prices and etc. - too much responsibility to give this to stores.
Also as POS is usually used to serve customers, for PO creation makes sense to use D365 Mobile app or PowerApp.