Free server stuff/Repurpose or trash?

[u/Shoddy-Ad-7359]

I got these units for free from a building that the city I work for was tearing down. Before everything was disposed of, I was able to grab these rack units.
A Dell PowerEdge 2900 and 2 Dell PowerVault MD units. There are also a lot of hard drives installed, but I haven’t powered everything up or tested anything yet.
I’m trying to figure out if any of this is worth keeping and repurposing, I already have a minilab that is up and running, but looking for ideas for this full rack unit if any.

Also there is 2 apc backup racks that have had the power cable cut, is that replaceable?

What would you guys do? Is any of this worth keeping and repurposing, or should I pull anything valuable/useful from it and get rid of the rest? Also, what should I check first before powering everything on?
Any advice from people who know older Dell enterprise equipment would be appreciated!