"I am from Scotland."
Translation:Tha mi à Alba.
Because when the predicate (the thing that goes after the verb to be, ie. in the sentence I am from Scotland the from Scotland part) is not a noun phrase, then typically the verb bi (tha, (bh)eil, bidh, bha, robh, etc.) is used and not the copula is.
You use is mise … only to say who you are (and only with definite noun phrases: is mise an tidsear I am the teacher but not I am a teacher – for that you use yet another construction: is e tidsear a th’ annam). And not to say where you are from, what you are like, how you are, etc. – for that you use tha.