There's a version of tar on FreeDOS, but the de facto standard archiver on DOS is Zip and Unzip.

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Open Source Way

Zip and Unzip are installed in FreeDOS 1.3 RC4 by default. Zip is a handy way to make a backup copy of your work or to release a "package" to use in a future FreeDOS distribution. ZIP and UNZIP use a Unix-like command line, so you can combine options behind the dash.

How to archive files on FreeDOS | Opensource.com