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.
This is a jukugo word that uses the on'yomi readings of the kanji. You should be able to read this on your own.
数年間
several years
数年先
several years ahead
数年前
several years ago
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.