To describe your background in the way you have explained, you could say: "I'm of mixed heritage. My mother is from Country A, my father is from Country B, and I was born in Country B. I lived there for a few years before moving to my mother's country." Alternatively, you could say: "I come from a mixed background. My mother is from Country A, my father is from Country B, and I was born in Country B. I spent a few years there before moving to my mother's country." As for an appropriate term to describe being "mixed," there are a few options that you could use depending on your personal preference. Some people prefer the term "multiracial," while others may use "biracial" or "mixed-race." Ultimately, it is up to you to choose the term that you feel most comfortable with.

As far as I know, we have no single word for this. The word "mixed" has racial overtones. It does NOT say that your parents come from different places. Use it only if race is the thing you want to emphasize. Instead, I recommend using words that emphasize your parents coming from different places and cultures. For example, "I'm half Indian and half Portuguese".