Hi @zajacjos,
Here is a step-by-step walkthrough of the setup, if that helps?
I will update this post with some screenshots as well.
1. When an item is created
a. Use the Site Address you want
b. Use your Project Numbers list

2. Add Initialize variable action
a. Use ProjectNumber as Name
b. Select Type String
c. Use Project# as value

3. Add Initialize variable action
a. Use Title as Name
b. Select Type String
c. Use Title as value

4. Add Initialize variable action
a. Use FolderStructureArray as Name
b. Select Type Array
c. Use an array like below as value
[
"1.Proposal",
"2.Quote",
"3.Purchase Order"
]

5. Add an apply to each.
a. Use the FolderStructureArray in the Select an output from previous steps
6. Add an Create new folder (within the apply to each)
This will create the folder structure based on the items of the array
a. Select Site Address
b. Select the Library, Project Folders
c. Use the following value for the Folder Path
/@{variables('ProjectNumber')}_@{variables('Title')}/@{item()}

7. Add a Copy Folder action
This action only copies the OneNote to the new Project Folder location
a. Select Current Site Address
b. Select the Location of the OneNote template
/Project Folders/Template OneNote
c. Select Destination Site Address
d. Select the Destination of the OneNote tempalte
/Project Folders/@{variables('ProjectNumber')}_@{variables('Title')}

8. Add a Send an HTTP request
This action is to retrieve the Odata type value for the next action
a. Select the Site Address
b. Use the GET Method
c. Use the following URI
_api/web/GetFolderByServerRelativeUrl('/sites/automation/@{outputs('Copy_folder')?['body/Path']}')/ListItemAllFields
d. Use the following Headers
{
"Accept": "application/json;odata=verbose",
"Content-Type": "application/json;odata=verbose"
}

9. Add a Send an HTTP request
With this action we rename the OneNote folder
a. Select the Site Address
b. Use the POST Method
c. Use the following URI
_api/web/GetFolderByServerRelativeUrl('/sites/automation/@{outputs('Copy_folder')?['body/Path']}')/ListItemAllFields
d. Use the following Headers
{
"Accept": "application/json;odata=verbose",
"Content-Type": "application/json;odata=verbose",
"If-Match": "*",
"X-HTTP-Method": "MERGE"
}
e. Use the following Body
{
"__metadata": {
"type": "@{body('Send_an_HTTP_request_to_SharePoint')['d']['__metadata']['type']}"
},
"Title": "@{variables('ProjectNumber')}_@{variables('Title')}",
"FileLeafRef": "@{variables('ProjectNumber')}-@{variables('Title')}"
}
