Unique Number to each item purchased

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New to shopify 

 My business sells entries to online competitions . 


 I need to find a way to add a unique number to each item purchased. 

So say if a customer purchases 5 tickets for the same competition, they need to receive 5 separate numbers in there order conformation. 


With some competitions having over 1500 tickets , I cant use the different variant's as an option . 

I can also not use the gigs/events apps as they charge 1 usd per sale and my tickets are mostly 0.99 gbp per ticket. The apps also do way more than I need. 


Please can anyone help me . this is the only thing stopping my site for launching . 


Thanks guys .