Match all after 8 or 11 characters

I am trying to match and get all words after a 8 or 11 character word, but i am stuck.
Form has a field which can have digits or alphanumeric characters.

I can solve this by using : (?<=\d{9}).*

But I can get correct match for below cases :

The highlighted field may have 8 or 11 alphanumeric characters.
(?<=[A-Z0-9]{11}).* or (?<=[A-Z0-9]{8}).* how can combine and create an expression to check the field and match the rest if it is 8 or 11 and match always ABC DEFG HIJK LMNOPR ST UVYXZ

Or maybe you can suggest something totally different to match ABC DEFG HIJK LMNOPR ST UVYXZ

Does this question involve Directory Opus? That looks like something else.

(Not just that this looks off-topic for our forum, but RegEx can also be slightly different in different software, depending on the flavor of regex in use, so answers we give here may not work in whatever that is.)