Labor theory of value is a Marxist idea, not an Adam Smith idea. Internet Marxists sometimes point to a passage in The Wealth of Nations to suggest that Smith also supported a labor theory of value, but this is—in the most generous interpretation—a misreading. Smith says that the value of a thing can be measured by how much labor it can be exchanged for: an exchange theory of value, not a labor theory of value (which says the value of a thing is based on how much labor it takes to create).

Use value or exchange value?

I was hesitant to elaborate there, because the relationship between effort and value is quite complex.

For instance, you can put a lot of effort into something, without creating any value for yourself or for others. But it is often true that things of utility need a sufficient amount of compounded effort behind them before they become valuable, otherwise they are common and easy to obtain. Value is necessarily relative.