The Salesforce Campaign token type in Marketo, much like the Image token type, is a dropdown token. It will display SFDC campaigns and will allow you to select which campaign you will want to sync your leads to. As you may know, Jeto cannot interact with dropdown tokens.
You can, however, create a plain text type token for Jeto and request the SFDC Campaign ID (not the entire URL or the SFDC Campaign name; it must be the ID, which is easily located in the URL as outlined below). In your Marketo flow steps, you will use the "Add to SFDC Campaign" step and in the Campaign field, you will use your text token. Here is an example of how you could create this in Marketo and Jeto:
1 - Create your text token to capture the SFDC ID:
2 - Add you sync flow step in Marketo and use your text token in the Campaign field:
3- Create the matching field in Jeto to capture the ID:
Here is an example of the value that the Collaborator needs to put into Jeto: