PellesC use 'PECOFF' object format (that is a deviated type of standard COFF) developed by MS.
You can convert OMF libraries to PECOFF using the POLIB utility. From PellesC help:
Convert an OMF import library to COFF with POLIB [4.00]
You can use POLIB to convert an import library in OMF format (Borland) to COFF (Pelles C, Microsoft). When you do, use the following syntax:
POLIB OMF-library /OUT:library
The OMF-library argument specifies the name of an import library in OMF format.
The result will be written to the file named library.
Always read help please.
Of course, as Akko said, you can't link 32bits and 64bits code (but I immagine you meant 64bit compiler not generated code).