I purchased my grandson's iphone 11 but donot know the appleID or password

You will need the Apple ID and password to make the phone usable. This is what your grandson should have done→What to do before you sell, give away, or trade in your iPhone, iPad, or iPod touch - Apple Support and he can still do it.

If the phone says Disabled, this is what you need to do. See this Apple support link→If you forgot the passcode on your iPhone, or your iPhone is disabled - Apple Support

Or watch this companion video ⬇️

After that finishes you will need the Apple ID and password (different from the phone’s passcode) that was used to enable Activation Lock, assuming it was. But the phone will tell you that when you set it up.

After my husband died I tried to get into the phone and used the codes wrong to many times