If you check Support and Help rules you’ll find your release is not a supported release here, being EOL or EOSS (depending on architecture) its now supported only by Canonical (as are 18.04 & 20.04 which release-upgrades will mandate you go though).
The only supported method for this site is to install a supported release and restore your data, as we can’t help you with the harder upgrades you need (16.04 to 18.04, then 18.04 to 20.04) if we’re to remain within site rules, though it’ll be less troublesome with the easier final upgrade to 22.04.
You’ve left it late for an easy release-upgrade path.
You didn’t provide architecture details; but 16.04 is End of Life for some, and End of Standard Support for others, which makes a difference in what is currently available, and where data can be found.
Mirrors are free to drop support once EOL is reached, with some doing it at the earlier EOSS, so you need to account for that too in applying upgrades.
Either way we cannot help with your current off-topic 16.04 needs.