I have other articles with datasets in MEV and TXT formats. How do I command R to recognize those formats? Thank you.

Do you perhaps mean MeV (https://doi.org/10.1093/bioinformatics/btr490)? As far as I know, MeV files cannot be read into R -- they can only be read by MeV itself.

Text (TXT) files can be read by read.table.