Impossible to import my old data from outlook 2011 to new outlook 2021

Hello,

I work on Mac OS Ventura. I've been working for a non profit since 25 years so I have many old mails and it's very important for me.

I've contacted many times the support but there is no solution to import my old data from outlook 2011 to new outlook 2021.

Can you please find a solution.

Thank you very much.

Valérie Dutin