link them together, and use them either as 1 large drive or as 30 separate drives
No.
SATA, some of them, but not all...
with something like this
With PATA (often still called IDE) ... At one time, you can only use two drives on one cable.
One choice might be to get
something like this for your drives, but you will only be able to have two drives operating at once, per ide cable.
Note... though they say it will work, these trays might not work with all drives.
Presumably one of your drives will be your boot drive and will not be swappable.
That means the most you could have in trays, available to swap would be three...
You will find this is, even at $20/drive, kinda spendy, for that many drives and you may wish to pursue other options.
One of them might be
Apricorn's Drivewire Universal HDD Adapter
This would be a "one at a time" solution, via usb.
This is a similar solution.
I have seen "docking stations" that might feel a little more substantial, but they seem to be for SATA only. (I say seem, only because I have never seen one for PATA).
With these you are also limited to 2.5" or 3.5" drives, where the Apricorn device can also handle the older larger drives.
(since the drive itself does not slide into some kind of socket... rather the device simply connects by cable).
Part of the issue behind the cable solution is that the 3.5" (and larger) have the power supplied through the molex connector.
That makes a "socket" solution more difficult.