Create a third JSON files from data in 2 JSON files using vb.net

I have 2 JSON files that are attachments data.txt has "YEAR":"ISSN": and Impact.txt has "YEAR": "ISSN": "IMPACT The Impact.txt file has over 10,000 rows the data.txt has less than 200. I need a third json file that has YEAR, ISSN, IMPACT only for the items on the data.txt file. be careful the ISSN has duplicated based upon the year. So it only unique based upon ISSN and YEAR. I would like it done without a loop. I can't see looping a 10,000 item object 100's and 100's of times. Using Newtonsoft.Json is fine. I need the fastest execution possible since this will be used in a live web app