If you want to you “我是从” it’s nevertheless more natural to say 我是从××来的, or you can say 我是××人, or 我来自××.

The direct translation will be: I am from = 我是從____來的 I come from = 我來自______ EX: I am from Brazil (我是從巴西來的) I come from Brazil (我來自巴西) However, as Demian puts, it is more nature to say 我是_____人 (EX: 我是巴西人)

'I am from' means 我是從 better than 我來自. You can use "I come from" to represent "我來自"