iphoto to photos

I did do a search on here, but found no help. I have almost 3,000 photos. When iphoto became photos did every picture go to the photos library? Sometimes it seems I can only find them on iphoto. I want to get rid of iphoto now and only use photos, how do I know for sure all of my pictures will be saved in photos?
I can only find the iphoto library.

Instructions here.

http://osxdaily.com/2015/04/17/move-iphoto-library-to-photos-mac/

Thank you, but when I do this : Relaunch the Photos app and immediately hold down the Option key until you see the Library selection screen, then choose one of the following options:

This does not show up

I dont know why...............

Should be a menu to choose between the two apps. What do you get? What OS are you using?

royalpei said:

Thank you, but when I do this : Relaunch the Photos app and immediately hold down the Option key

This does not show up View attachment 23695

I dont know why...............

Click to expand...

Because you're doing it wrong. Hold down the option key BEFORE AND DURING the launching of Photos (or iPhoto for that matter).