Hello Roselyne,
Thanks for using the Events Calendar.
Here on the pre-sales forum, I’m afraid we do not provide technical support. I would ask that you take any technical support questions across to our wordpress.org forum – our staff scan it periodically and other community members may also be able to help out.
The Events Calendar
If you have purchased a plugin from us, please login and post in the premium forums for that plugin and we can help you out there:
https://theeventscalendar.com/support/forums/
To get you started, I believe migrating your database would maybe be the easiest in this case. I’m not sure what custom fields you are using, but migrating the wp_posts and wp_postmeta table should do it.
In case you want the dates & times to appear properly, then I’m afraid you will need to do that manually one at a time.
Thanks again for reaching out!
Cheers,
Andras