Compatibility of iMac G3 hard drives, to try to recover data

I have an old iMac 400MHz slot-loading G3 model #M5521 that won't power up (think it's a dead power supply), and I'm trying to get the data off my hard drive. I also happen to have a 333MHz tray-loading G3 model #M4984 and am wondering if I can put the HD from the 400MHz into the 333MHz, just to use to boot up and back up my data onto a flash drive.

Here are the specs: iMac #1 (the one with all my data on it): 400MHz slot-loading G3, Model #M5521, 20.4GB hard drive (may not be the original HD - think it originally came with a 13GB), 320MB memory (256 and 64 cards), dvd drive, serial #RN9445BXHCW, and is running OS 10.3.9. The hard drive says on it: Maxtor HD model # 92049U3, 20.4GB, manufactured 15 July 2000.

iMac #2: 333MHz tray-loading G3, Model #M4984, 6GB hard drive, 288MB memory, CD drive, serial #XB9361VUGSQ, and is running OS 9.2.2.

The questions we have are whether the 400MHZ iMac hard drive can be put into the 333MHz iMac and, if so, whether it would be able to boot/run it given it is running OS 10.3.9. We are trying to do this ourselves, as we are money-limited, and my husband is capable of changing the hard drives, however the 333MHz iMac is the only other machine/method we have to use to try to recover the data. Any info you could provide on the compatibility of the two hard drives/iMacs would be very much appreciated.

Thanks a lot, Cindi