Shimano lists 2 current Acera triple front derailleurs, both are top "swing" 3X9, AFAIK will work on 3X7. One is TS3 the other TS6, I don't know the difference. Shimano, as is common, doesn't provide a lot of specs. One can use the model # from Shimano site & google it...often retailers provide more specs. Just to be sure you might want to measure the chainline & also note # of teeth on chainrings since front derailleurs are designed to work best for a certain range, ie difference between # of teeth on large & small rings.
https://www.sheldonbrown.com/chainline.html
https://bike.shimano.com/en-US/produ...era-m3000.html