Batch edit or insert ranges of identifiers?

We are in the process of setting up Omeka Classic to act as our DAMS. I have inherited an install of Omeka Classic that already has several collections (with hundreds of items each) uploaded. The items in these older collections do not have identifiers, though, and dcterms:identifier is a required field if we are to share our digital collections with other digital libraries in the state.

Is there a way to batch add identifier numbers or ranges of identifier numbers to the metadata of items that already exist? I’ve tried the batch upload and bulk editor plugins to do this but haven’t yet been successful.

Many thanks!