add fluid to automatic transmition

Hello All,

I have suzuki eurswift sedan 2002
engine G13B
3 A/T

I am almost sure I have to add fluid to it.
Recomended Dexron III or similar.
But I don’t know what liquid is in there right now.
Could I assume mix simlar fluid will be OK.
OR
to flush all the A/T fluid?

Rgds.

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