Hi @ ClaireAllen,
Do you want to copy attachments of the item to SharePoint library when a new item is created ?
Or do you want to copy attachments of all items in SharePoint list to SharePoint library?
I have made a test on my side, If you want to copy attachments of the item to SharePoint library when a new item is created. please refer to steps below to create the flow to copy the attachments from a sharepoint list to SharePoint Document Library :
1. Add a trigger “When an item is created” of sharepoint connector, fill in the “Site Address” and “List Name” field.
2. Add action “Get attachments”, fill in the the “Site Address” and “List Name” field, choose the “ID” dynamic content of the trigger in the “Id” field.
3. Add an “Apply to each”, choose the “Body” dynamic content of the “Get attachments” in the input field.
4. Add action “Get attachment content” inside the “Apply to each”, fill in the “Site Address” and “List Name” field, choose the “ID” dynamic content of the trigger in the “Id” field, choose the “Id” dynamic content of the “Get attachments” in the “File Identifier” field.
5. Add action “Create file” under the “Get attachment content”, choose the “Site Address” and “Folder Path” field, choose the “DisplayName” dynamic content of “Get attachments” in the “File Name” field, choose the “Attachment content” dynamic content of “Get attachment content” in the “File content” field.

When I create an item with attachments in the list as below:

the flow would run successfully as below:

The attachment would be created in the document as delow:

If you want to copy attachments of all items in SharePoint list to SharePoint library, You could modify the trigger to “Manually trigger a flow”, and add action “Get items” of Sharepoint connector ,and then copy all attachments in the list to SharePoint library.
Regards,
Alice Zhang