I can’t turn on the tracking settings in my iPhone SE

If your Apple ID is under age 18 by birth year, the “Allow Apps to Request to Track” setting cant be turned on.

⇢ If an app asks to track your activity - Apple Support

As shown in your screenshot:

"This setting cannot be changed because your Apple ID does not meet the minimum age requirements."

In that case, you’d need to lie about your Apple ID birth date, which would violate Apple’s terms and conditions. Also, it’s important to enter your accurate birth date as it serves various purposes, and might be used to reset your password.