Apprentice ship or Trainee system - include a clause in the appointment letter that they need to work for 1 year to get the confirmation letter?

Dear All, We need to hire candidates for a department,so most of the time freshers. We are planning to opt for an apprenticeship/Trainee.

I researched, that for an apprenticeship, it should be a regular process. we need to hire apprentices regularly. But this will be a concern if fewer projects.
In the case of trainees, based on the requirement we can hire them, PF, ESI, Gratuity, the bonus will be applicable?
But we can stop the recruitment on a need basis.
Can we include a clause in the appointment letter that they need to work for 1 year to get the confirmation letter. This is to reduce the attrition. Please advise

Usage of the term Apprentice has legal connotations, primarily they have to be apprentice as per the Apprentices Act 1961 and there is a prescribed method of training to be followed. This does not seem to be the case. You can call them as Trainees.
In the appointment order you can specify that at the end of one year training the trainees will be considered for regular appointment (as Probationer/confirmed employee). It is not likely that this will help in containing attrition.