Take a look at the original sentence again:
Ingie looked at his wife's collection of cookbooks and
sighed, although there were thousands of
recipes for delicious meals, he knew Valerie would want to order another
pepperoni and mushroom pizza for dinner.
You wanted to fix it this way:
Ingie looked at his wife's collection of cookbooks and
sighed; Although there were thousands of
recipes for delicious meals, he knew Valerie would want to order another
pepperoni and mushroom pizza for dinner.
A semicolon is an excellent way to join two complete sentences. You must, however, use the semicolon correctly. Do not capitalize the word that follows the semicolon unless it is a proper noun, one that is always capitalized.
You might want to consult the rules for fixing comma splices and fused sentences.
Go back to the sentence to try again.