YOU SAID:

I wish I had a very long leg

INTO JAPANESE

とても長い脚があればいいのに

BACK INTO ENGLISH

I wish I had very long legs

INTO JAPANESE

足がとても長いといいのに

BACK INTO ENGLISH

I wish my legs were very long

INTO JAPANESE

足がとても長かったらいいのに

BACK INTO ENGLISH

I wish my legs were very long