I'm curious as to how i can create a workflow in SharePoint designer that can delete ( or erase content) in an objects list? Does anyone have an idea?
Based on your comments (namely that this should apply to already existing items), I would recommend not using a workflow, but a Retention policy instead. One of the advantages to this, is that cancelling the workflow will prevent the item from being deleted at the correct time.
SharePoint Mavern has a really good guide here (https://sharepointmaven.com/set-retention-deletion-policies-files-folders-sharepoint/). You're probably looking for #3 Document Libraries.
The gist of Retention is that you can set a time period to keep an item, and on the expiration date the item is deleted. Below you can see some of the options available when configuring the policy.