Whats the correct way to implement dockerfile if the requirements.txt exist in parent-child folder

Question

Issue in creating a dockerfile as I am getting a error that the requirements.txt file is not existing however it exists in the parent folder

I have a directory with the below given structure

Folder
|
|
--requirements.txt
|
|
--Sub_Folder
     |
     |
     --Dockerfile

However when I am trying to copy requirements.txt I am getting error that the file doesn't exist

COPY ..\requirements.txt .\