Do you use teamcenter? The I-Deas file will it be a package file, parasolid, XPK, file model file or an I-Deas archive file? Do you have the Content Migration Manager for converting I-Deas data to NX in teamcenter?
Do you need part history? If not have them send you a XPK file. On their side is should be file interoperate and export a NX package file. A parasolid file will work well also.