How to do 3-way-SLI with 36v battery and ups

i have buy 3500kva is of 36v

shopkeeper said i have to use tri-way sli... of 3 batteries

so plz tell me battery recommendation...

It should be 3500VA, i assume.

As you told, it is 36V UPS so it will need 03 batteries in series because each battery is 12V. Now you need to calculate your battery capacity in amp-hour. This calculation is simple but I need to know your maximum load and your required backup time in hours.