Hello Atul,
PR is an internal document that User/Department gives to Purchase department for giving details about the requirement that is why SAP doesn't provide free indicator in this transaction me51n.
As PO is an external document and we need to provide the price for making a PO, so that is why SAP provides field in me21n from marking free indicators.
As pricing available in PO is not available in Me51n in the same way free indicator is not availble.
Regards
