Create and or Update Sharepoint List from Unique ID pulled from Survey123

[SunshineK]

Hi Team, 

I am trying to create a two part flow from a survey in survey123 - and cannot figure out where I am going wrong.
It seems as though I fix a problem then create another one.

What I want to do:
When a survey is submitted I want to either create an item in SharePoint list if the 'Unique ID' is not in the list... or if the 'Unique ID' is in the list I want to update an item in the SharePoint list.
(the 'Unique ID' is a number that I pull back from Survey123)

Flow (Part1): 

Flow (Part 1) PROBLEM:
Scenario – there is currently no item in the sharepoint list.

Error message:

The 'inputs.parameters' of workflow operation 'Update_item' of type 'OpenApiConnection' is not valid. Error details: Input parameter 'id' is required to be of type 'Integer/int64'. The runtime value '"e507edbb-6445-4a85-b9f1-11dd9c73b713"' to be converted doesn't have the expected format 'Integer/int64'.

Flow (Part 2): 

Flow (Part 2) PROBLEM:

Scenario: there is already an item in the sharepoint list that I want to update (ie same unique ID)

 I have also tried both parts above with the condition set as: 

length(body('Get_items_x')?['Unique_ID'])

equal to '0'

An error message comes up - something to do with string and integar. 

I have tried multiple different ways over the last few days and gone through these posts with no luck of finding a solution. 

Please, any help would be fantastic. 

If I can't do it this way, I would be more than happy to create a new item each time and delete the 'older' duplicate unique Id. 

Cheers, 

Summer