hmmm,
i would say get the same ones that you already have on, but how do you tell?
Good question!!
No idea,lol. You could maybe take a string from your guitar to a shop and ask them if they can measure it if you have not got a measure device for strings.
I use "extra light" guage for my guitar the 1st E ( thinnest) is 0.010" or 0.25mm
you could try buying medium gauge and try them. then decide from their . If they hurt your fingers too much then go for a lighter one next time but if you do keep playing with them your fingers will toughen up more anyway and you will not notice any pain.
really it depends what sort of sound you want.
A really light guage gives a tinnier sort of sound where heavier gauges are duller,damper sort of sounds.
So, if I were you, I would go for medium if you cannot find out what you are used to playing with.
And remember, when you change your strings your guitar will sound completely different until the new string settle down.
Ken
ye get some that are cut out for the job and others just get by from pretending