I got a list of songs to buy from the customer, for example, "21301896."
By typing the number into the search field, the system displays such a message to me.
…You’ve ventured too far out into the desert! Try clearing your filters.
We couldn’t find any results for your search. Use more generic words or double check your spelling…
WHAT TO DO? HOW TO LOOK THESE SONGS !!! HELP!!!
Is this the track you are looking for?
https://audiojungle.net/item/mood/21301896
Since Envato decided to make the item id number non-searchable for whatever reason, the only way to use these id numbers to find a track is to put it in a URL, like so:
htttp://audiojungle.net/item/x/idnumber
You replace “idnumber” with the actual id number of course.
Like PurpleFogSound said, take ANY link to a song and just replace the number, for example:
“https://audiojungle.net/item/glitch-futuristic-inspiration/21346316”
Replace the number at the end with your number.
“https://audiojungle.net/item/glitch-futuristic-inspiration/21301896”
No need to change the text (the original title) as the site only cares about the last number.
Hey, @PurpleFogSound and @Flumen solution are the best, but you can also search on google for these items if you type for example this: audiojungle item 21301896. 
https://goo.gl/VX1GxL