Hi @Nick_K_H, does your service accept these files in individual requests? If so, you can split our files into individual n8n items with one file each:
If your service requires all files in a single request in separate fields I am afraid you’d have to create multiple routes in your workflow that handle the different possible options. You could use a Filter node here checking if {{ Object.keys($binary).length }} equals 2, if so connect an HTTP Request node processing attachment_0 and attachment_1. Another Filter node checking if {{ Object.keys($binary).length }} equals 3, if so connect to an HTTP Request node processing attachment_0, attachment_1, and attachment_2 and so on until you have covered the expected cases.
In theory you could alternatively use a bit of code (which allows calling the http request functionality in n8n) though I do unfortunately not have a snippet ready for this.