HI Sandrine, A similar ask was posted earlier here : https://salesforce.stackexchange.com/questions/147030/can-we-convert-a-multi-select-picklist-value-into-single-select-picklist-value
We will be losing data if Changing from multi Picklist to any other type. It's not possible to avoid while conversion but we can do with apex data loader with minimal risk. > Take a backup > convert to picklist > Remove multi select to single value in csv file with respect to your requirement > upload into salesforce.
If this information helps, please mark the answer as best. Thank you
A similar ask was posted earlier here : https://salesforce.stackexchange.com/questions/147030/can-we-convert-a-multi-select-picklist-value-into-single-select-picklist-value
We will be losing data if Changing from multi Picklist to any other type. It's not possible to avoid while conversion but we can do with apex data loader with minimal risk.
> Take a backup
> convert to picklist
> Remove multi select to single value in csv file with respect to your requirement
> upload into salesforce.
If this information helps, please mark the answer as best. Thank you