Either form is correct.

If you have just finished this period of apprenticeship, it is fine to use the present perfect (have had)

If this period ended some time ago, and you have done other things since then, you should use the past (had).

If in doubt, it is generally better to use the past form.

By the way, the phrase "During my three years as apprenticeships," does not make sense. It should either be "During my three years as an apprentice," or "During my three years of apprenticeship" (if you had one apprenticeship) or "apprenticeships" (if you had more than one).

had             an event was just in the past.
have had     an event was in the past and still running, or its influences are running up till now.

If the time is clear u have to use simple past"had",otherwise,u should use present perfect"have had".

Thank you very much for your help.

The present perfect has no equivalent in french Its employment expresses a past that has a relation with the present. So this is an action that start  in the past but which still or has repercussions in the present:

I have always lived here  (J'ai toujours vécu ici). le passé composé -j'ai vécu-   est  un passé qui se prolonge  dans le temps et traduit "The present perfect".

I have been learning English for two years. (j'apprends l'Anglais depuis deux ans)  -j'apprends- est un présent qui se prolonge  également dans le temps et traduit  "The present perfect".

  Je crois que "The present perfect" peut être exprimé   par un passé composé ou par un présent mais dans un contexte qui reflète la continuité dans le temps