How to convert files from Cadence to Eagle CAD?
Importing from different CAD packages often has issues.  

There are three main parts: schematics, libraries (containing schematic symbols and PCB footprints) and PCB layout.

CAD packages can import them as individual's but do not necessarily import all three as a linked package.  This can cause issues for future maintenance of the boards and manufacturing issues due to footprint's not being verified and validated fully during the translation.

A safer and often shorter in the long term approach is to duplicate the library parts and verify all symbols and foot prints, followed be re-entering the schematics, (this will be trivial once all the parts are in the library) and re-laying out the PCB using the existing PCB files as a guide.

This is the only way you can be certain all parts used are correct, and you have not created or lost any artefacts during the PCB importation process.