I want to replace the. I want to replace the upper and lower heating elements on an older modle

Question

I want to replace the upper and lower heating elements on an older modle water heater, MOR-FLO Model SD50. However when I removed the old theromstats expecting to see the s***w out elements underneath the thermostat, there wasn't any there.I am at a loss as to what to do to repair this old tank.Any suggestions?Thank you.