That's an 'Oldie, but Goodie'!!
You may have to do some 'reverse engineering' to determine what size pump you need. How many total Jet Nozzles are on the 2 rings? Are they 1/4" or 3/4" nozzles? What was the spray height and throw when the fountain was operational? What is the size of the center geyser? And what do the supply lines marked on the photo lead to?
Post that info and the pump size can be approximated.
"Everybody is ignorant, only on different subjects." - Will Rogers