It is convenient for him to call on her.
而I am convenient to call on him的用法是错误的。
It will be convenient to know her.
一是表示想要认识她不难。二是表示认识她之后将来有许多便利。
It will be convenient that I shall call at four o'clock.
这种表述是错误的。应改为It will be convenient for me to call at four o'clock.