Sort in Excel and replacing chars

I have 18000+ rows in excel, each row has a different value on it. For Example:

PTH03020WAZ
PTH03030WAZ
PTH03030WAD
PTH03050WAZ
PTH03050WAD
PTH03050WAH.
PTH03060WAZ
PTH03060WAD
PTH03060WAH
PTH03060WAH.

Now if the first 8 chars are the same, I want to remove the remaining chars and replace with “(Space) Series”

Can anyone help with this?!

Thank you in advance!

Ross