Rooted or not, I can not figure out I don't know if someone already rooted my Samsung Sm-t530.
Can somebody help me?

I just find some files like

Knox emulated
Emulated
Extsdcard
Sdcard
Mnt
Storage/emulated
Dev/emulated


And i cannot find Imei.
Download a root check app or look at your settings and see if you have anything like supersu installed. There is many root check apps on the play store which you can use. You can check your imei number in the phone near the battery (or under the battery if it's a removal battery).