我记不清这是我给你寄的第几封信 用英语怎么说?

I don't remember how many letters i have sent to you
我记不清给你寄了多少封信了 .
I don't remember what is the number of the letters that i have sent you.我记不清一共给你寄了多少封信了.
I don't remember what is the number of this letter that i have sent you 我记不清这是我给你寄的第几封信了?
------smiling and Say yes (hahaha yeS

I can not remember This is what I send to you the first few letters

I can't recall how many times I've sent you letters before.