1.Take a text input in the same screen which you want to display Id
place the below syntax in the default property
Last(Sort('User Information',ID)).ID
user information is name of the list in sharepoint.
after go to visible property of textinput and make it false.
Write the text whatever is required
for example,
"Your Generic email account creation request has been submitted successfully to the IT Support Team. Thank you! Reference No. " &TextInput2_1.Text
here TextInput2_1 is the text input's name you have made invisible
Please try it and let me know
It worked for me.
Thanks,
Usha.