This is not just one mod. You need to download all of the mods below and put them in one folder together.
Once you've done that, go in game and press F1. The modloader should appear. Type "Drive" , press enter, and if you see the 9 drive bar number appear you should be good to go.

Modloader: https://www.nexusmods.com/kingdomhearts3/mods/938
Valor: https://www.nexusmods.com/kingdomhearts3/mods/993
Wisdom: https://www.nexusmods.com/kingdomhearts3/mods/1553
Wisdom Quick Run: https://www.nexusmods.com/kingdomhearts3/mods/1971
Master: https://www.nexusmods.com/kingdomhearts3/mods/1585
Final: https://www.nexusmods.com/kingdomhearts3/mods/1332
Final Form Glide: https://www.nexusmods.com/kingdomhearts3/mods/885
Anti: https://www.nexusmods.com/kingdomhearts3/mods/1715
Drive SFX: https://www.nexusmods.com/kingdomhearts3/mods/1111
KH2 Hud: https://www.nexusmods.com/kingdomhearts3/mods/478

This mod also adds in all of the mechanics the forms had in KH2.
Valor runs faster and cannot guard-cancel out of an attack, but instead can press Square to perform a ground/ air combo modifier.
Wisdom has Quick Run instead of Dodge Roll
Master's double jump gives you some height and invincibility
Final can idle while gliding if Circle is held after a jump
Anti points accumulate exactly like KH2

This mod supports both KH3 and KH2 Sora.
If you're KH2 Sora, your clothes will change color based on the form you choose.
You can only Dual-Wield if you have Kingdom Key, although using any other keyblade does not affect the system otherwise.

If you go in to a form, and then try to go in to that form again, you will revert and lose drive bars respective to the form you were in.
Valor and Wisdom = 3, Master = 4, Final = 5
If you go in to a form, then another form, and then revert, you will lose a combined amount of bars equal to the forms you went in to.