Which one is correct?

The is used to refer to specific or particular nouns; a/an is used to modify non-specific or non-particular nouns. We call the the definite article and a/an the indefinite article. For example, if I say, "Let's read the book," I mean a specific book.

The thing you need to ask yourself is how many complete five volume shop manuals there are. If there are many then it's a, if there's only one it's the.

Thank you for the answer!

Take a look here (in Description)
https://www.amazon.com/1973-Ford-Truck-Shop-Manual-ebook/dp/B0838N3PZP

https://www.amazon.com/1978-Ford-Truck-Shop-Manual/dp/1603710868

(This is a complete or It is the complete )

in what situation sounds right?

It looks fairly unique, so I'd say the.

You might also consider placing a hyphen between the word "five" and "volume."

Thank you very much! The issue is closed.

Thank you