This is a fairly direct translation. The code should be pretty straightforward:
@ECHO OFF
SET LookForFile="C:\Path\To\File.txt"
:CheckForFile
IF EXIST %LookForFile% GOTO FoundIt
REM If we get here, the file is not found.
REM Wait 60 seconds and then recheck.
REM If no delay is needed, comment/remove the timeout line.
TIMEOUT /T 60 >nul
GOTO CheckForFile
:FoundIt
ECHO Found: %LookForFile%
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