Six-hour training or Six hours' training

Which option is correct, or both are?

Six-hour training
Six hours' training

So, here it is my idea:

In the first case, the hyphened six-hour training works as a compound adjective and therefore the noun hour does not take the plural inflection, whereas in the second example hours is pluralized because it is not a compound form and it takes the genitive 's as any plural noun does.

Any idea/correction would be much appreciated!

My thoughts are:

Six-hour training -- you would usually see this as an adjectival phrase referring to something else, such as 'six-hour training session', or six-hour training day'. I am not sure that you need to use the hyphen in these phrases.

Your description of the second option is correct, in my opinion.

Six-hour training or Six hours' training

Which option is correct, or both are?

A six-hour training
Six hours' training [Better, Six hours of training]

So, here it is my idea:

In the first case, the hyphened six-hour training works as a compound adjective and therefore the noun hour does not take the plural inflection, whereas in the second example hours is pluralized because is not a compound form and it takes the genitive 's as any plural noun does.

Any idea/correction would be much appreciated!

Six-hour training or Six hours' training

Which option is correct, or both are are both?

Six-hour training
Six hours' training

So, here it is my idea:

In the first case, the hyphened six-hour training works as a compound adjective and therefore the noun hour does not take the plural inflection, whereas in the second example hours is pluralized because it is not a compound form and it takes the genitive 's as any plural noun does.

Any idea/correction would be much appreciated!

 Just use 6 hour training