Recover data from failed RAID 5 Dell Poweredge T710 Server

Very important data on RAID 5 array on poweredge T710 server - how can I get the data back? Willing to spend money to do it (eg buy a replacement system and swap the disks in), would prefer not to pay tens of thousands of dollars to a third-party data restoration service, but may have to consider it if can't DIY. Data are important.

Does it make the most sense to first try to:

1. Get the current system working, since it has configuration information already in it. So far, haven't succeeded at this.
2. Remove the drives and clone them using some kind of hardware/software designed for the purpose to make sure that the data are safe. If so, what kind of hardware/software should be used. Currently in a mostly Mac environment, and don't have any modern PCs, though could get one I suppose.
3. Buy a used T710 (they seem to be available on eBay for <$1000), install the RAID drives there, try to get at the data that way.
4. Some other approach.

Current behavior of system: There are a variety of confusing and inconsistent behaviors. Not sure which ones are relevant.

On first powerup in many years, the system came up on monitor to indicate a bios error of some kind. Tried to reboot, this time the system failed to start at all. When pressing power button, nothing at all happens.

Replaced the motherboard battery.

The system then powered up once. Was able to enter the configuration utility. See below for all the screenshots I was able to capture. Most salient points seem to be that the system is RAID 5, and two drives are considered 'missing' by the system, though they are physically present, and have yellow/orange lights illuminated.

After this I hit ctrl-alt-delete to restart the system, but it would not restart. It just seemed to 'go dead' and would no longer power up, even after pressing the power button, power cycling, turning off power and waiting several minutes and attempting again. This is what it was doing previously, and now it won't power on at all. Not sure what caused it to power on after I replaced the motherboard battery so that I could capture the images below (but glad that it did!).

I believe that the system was configured with Windows Server OS, but not certain, and not certain of version, further details (this system was from a long time ago).

Thank you for your help

Wow. This question. Another example of what not to do. You don't have appropriate backup methods in place. You don't know if your backups are any good and have no good way to test them. You have data that you claim is very important, yet you're looking for ways to recover the data without spending "thousands of dollars".

Either the data is important enough to spend whatever is necessary to recover it, or it isn't. If it is then start reaching out to data recovery companies. If it isn't, then keep tinkering around and risk losing the data forever. One or the other. There's no in between. Are any of the methods you proposed likely to help you recover the data? No. Are they likely to cause you to irretrievably lose the data? Yes.

A data recovery company is not going to need the entire server. They're going to need the drives. They'll tell you exactly what to send and how to send it. They have their own equipment (in a clean lab) to reconstruct the array and recover the data.