How will define weight type like kg / litter or others unit

[gusty sand]

It's up to you to decide in what unit are you storing.

[foggy lintel]

but there are no option to set unit

some product are unit type litter and some are kg and some are gm

In frontend need to know the unit type

[gusty sand]

I see. I don't think there's an option. You can create a feature request in github discussions