How to properly use an IF and GOTO statement

I have zero experience with writing batch files but my goal does not seem difficult. I'm trying to write a small script that will prompt a user to enter an ID number and then search a directory of .jpgs and copy any pictures containing the ID number to a separate directory. The .jpgs are names xxxxxx_zzz.jpg where xxxxxx is the ID number up to 6 digits and zzz is the sequence number. For example, one ID can have many pictures: 123456_001.jpg, 123456_002.jpg, 123456_003.jpg, etc.

I've played with several IF and GOTO commands, but I seem to be diverging from my goal. I know the two IF statements I currently am using below are garbage, but I left them in the syntax to convey the direction I think I should be moving in.

I can't get the IF statements to use the GOTO commands. I also don't think I fully understand how labels are supposed to work.

   @ECHO OFF
   CLS
:START
   DEL /q C:\Users\ADMIN\Desktop\temp\*.*
:GETINPUT
   set /p propkey=Enter the Property Key of pictures to retrieve.:
   IF EXIST C:\Users\ADMIN\Desktop\photos\*%propkey%_???.jpg GOTO Success
   IF "%propkey%"=="" ECHO No Property Key was entered. GOTO START
:Success
   ECHO Pictures from Property Key %propkey% will now be moved to the Temp folder on the Desktop. && PAUSE
   COPY "C:\Users\ADMIN\Desktop\photos\*%propkey%*.jpg" "C:\Users\ADMIN\Desktop\temp\"
   START C:\Users\ADMIN\Desktop\temp\
:END

Solution

Try this:

:Start
   @echo off
   cls
   :: store source folder
   set _sd=C:\Users\ADMIN\Desktop\photos
   :: store target folder
   set _td=C:\Users\ADMIN\Desktop\temp
:CheckFolders
   if not exist %_sd% echo Source folder not found.&goto End
   if not exist %_td% echo Target folder not found.&goto End
   :: wipe target folder
   del /q %_td%\*.*
:GetKey
   set /p _key=Enter the property key:
   if '%_key'=='' echo No property key entered. Please retry.&goto GetKey
   if not exist "%_sd%\*%_key%*.jpg" echo No photos matched the key.&goto End
   echo Copying pictures to %_td%...
   copy "%_sd%\*%_key%*.jpg" "%_td%"
:OpenFolder
   start "%windir%\explorer.exe" "%_td%"
:End

A label is a way to arbitrarily designate a line in a batch file. It is used by the GOTO command to change the usual top-to-bottom progression of command execution, specifying which line should be processed next. As you probably figured out, using IF commands in unison with GOTO allows for conditional processing, such as when values are met or errors are encountered.

Another use of a label could be for documentation or clarity. In my example above, "CheckFolders" isn't used by a GOTO, but it lets the programmer hint at what that section of code does.