how can i see my iphone bettery health

I don't know exactly how your battery was replaced, but I do remember reading somewhere that only a genuine Apple battery replaced by Apple will show battery health. A third-party battery, replaced by someone/somewhere other than Apple will not, unfortunately, show battery health. Hope this helps you!

If you had the battery replaced ANYWHERE other than at Apple or an Actual Apple Authorized Service Provider, they could not put an authentic battery in your iPhone. If this is what you did, you will NEVER be able to see Battery Health on your iPhone again.