it is my frist time to do sth / or doing sth/or do sth?

it is my frist time to do sth
序数词后面要接不定式
如：This is his second to come to New York.
He is the first to come and the last to leave.

楼上的错啦,这是不定式作主语的结构,it是形式主语:it's my first time to do sth.

一般情况下是:it's my first time to do sth. 但是有时候会 it is my first time did sth.
具体的看情况, 现在的高二书上有这个知识点.

it's my first time doing sth.

it's my first time to do sth