Can we assume that he got soft copies and not all hard copies?
Then it would depend on the format of the files that he got. DOC, PDF, TXT etc.
What is the file size or volume?
You can get over 250 gig memory the size of your pinky nail.
Yeah, now you can. If this guy started in the mid-90s, that was still fairly early in the CD-ROM storage era.
God, I hope so. If you can sneak out with 100 reams of paper daily, double sided, the security is worse than I think. A PDF of a text page is about 10-15K on average, so a gig to gig and a half a day, maybe 10 times that if images, either scanned or photographic. So your 256GB fingernail would last him 8 months to a year for text, again assuming 5 days / wk. Maybe one a month if images.