Hi,
If the supplier sells goods and they are sent from Turkey to North America, then these will be outside the scope of VAT which would be reflected on their invoice.
If they send goods over a value of £135 to you in the UK then it will depend who the importer of record is.
If the supplier is the importer of the goods in to the UK then they will need to charge UK VAT.
However, if you are the importer of the goods in to the UK, then the supplier will not charge VAT and it will be your responsibility to pay any import VAT on the goods once they enter the UK.
If the supplier sends goods to you in the UK and the value of the goods are below £135 then please see the guidance here:
Changes to VAT treatment of overseas goods sold to customers from 1 January 2021
Thank you.