Translation:The length of the side of this wallet is three inches.
There are many errors in this English translation. I suggest that a better translation is: "The side of this wallet is three inches long." or "The sides of this wallet are three inches long."
"the length of this wallet's side is three inches" - also there is an error when filling out the answer wuth the word bank creating a misspelling when using "wallet" and " 's "