Probably lots of info here if you do a search. I’ve always used Castrol Transmax Import ATF on my V6 rig with good results—takes around 3qts, I believe, to top it off after draining. 
 

There are varying opinions about whether ATF should be serviced if it’s been allowed to go a LONG time with no attention. FYI. 

Hello, I need to change the transmission fluid on my 1991 Toyota Warrior V6. Which transmission fluid should I use and what quantity? Are synthetic fluids superior?

https://toyotamotorhome.org/forums/index.php?/topic/206-1995-34l-5sp-4x4-bajarader-put-the-sawzall-down/#comment-672

With enough time, talent and cubic$$ anything is possible