Copying a field content to another, for 3k leads

Copying a field content to another, for 3k leads

Hello,

We need to update about 3k leads, as we used a custom text field when we started using Zoho. Now we need to copy the content of this custom field to a Zoho field. We could copy paste the content for each lead, but we have 3000 of them (and more with the contacts).

How could we automatize this in any way ?

Regards