Conversion of inp files to txt file format

The only software that can reliably work with .inp documents would be inPage, the very same software used to save these files in first place. It allows export to RTF format which you can open in almost every word processor and then export the text or manually copy and paste the text out. But it might well be possible that saving to plain text is also offered in inPage itself.

Open INP file    Open TXT file