Several Years
noun
When a number of years have passed you say that several years have passed! You don't want to say how many years, so just say several years.
すうねん
This is a jukugo word that uses the on'yomi readings of the kanji. You should be able to read this on your own.
日本に来てから、数年です。
It's been a few years since I came to Japan.
数年ぶりに、元パートナーに会いました。
I met a former partner for the first time in a few years.
あ、思い出しました？数年前に一回、コスプレのイベントでお会いしたことがあります。
Oh, did you just remember? We met once at a cosplay event a few years ago.