YOU SAID:

I will come to your moms house for a pair of pants

INTO JAPANESE

あなたのお母さんの家にズボンを買いに行きます

BACK INTO ENGLISH

I'm going to your mom's house to buy some pants

INTO JAPANESE

お母さんの家にズボンを買いに行くよ

BACK INTO ENGLISH

I'm going to buy pants at my mom's house

INTO JAPANESE

お母さんの家にパンツを買いに行きます

BACK INTO ENGLISH

I'm going to buy pants at my mom's house