I've gotten what you all sent here and that helped a lot! thank you!
However, I'm still having some troubles with the flow failing on different steps depending on what I try to fix..
Currently I have:
'PowerAppV2->Sendanemail(V2)'.Run(EmailListFlow.Text, SubjectEmailReqPick.Text, BodyEmailReqPick.Text, JSON(colPickUpID) )
1. On a button's OnSelect on PowerApps, I have:
2. When PowerApps Calls a flow
With 4 different text parameters:
- EmailList (with the emails I want to send)
- SubjectEmail
- BodyEmail
-colPickUpID (this is a collection with the ID's only, but the output ends up being something like:

3. Initialize Variable
4. Compose (which is what I'm having most trouble on)
This was an effort to converting the string of colPickUpID into an array
5. Big Loop - Apply to Each ID
The Outputs on "Apply to Each ID" is the outputs of compose from the step before
6. Get Attachments
Here I'm linking my sharepoint address and list. On the ID, I have the "apply to each ID"'s current item
7. Apply to each Attachment (inside the big loop)
The output selected in the Body of "get attachments"
8. Get attachemnt content, I have ID as current item from "apply to each ID" and File identifier as "get attachments, ID"

9. Append to array variable:

Name: Apply to each attachment, display name
Content Bytes: body(get attachments)
10. Lastly, the email
Where do you think could be the problem?
Thanks!