It should be fine. If you’re truly worried, go here:
https://ftp.heanet.ie/mirrors/linuxmint.com/stable/
And click the version of Linux Mint you downloaded - it’s probably 21.3 - and then download both sha256sum.txt and sha256sum.txt.gpg by right-clicking -> “save link as…” to download the files themselves.
After that, verify the iso you had in your downloads folder by following the instructions here:
https://linuxmint-installation-guide.readthedocs.io/en/latest/verify.html
Again, as long as you downloaded from one of the mirrors linked on the Linux Mint download page, you should be absolutely fine. This step is a just-in-case, for your personal ease of mind. It will, however, need you to open cmd.exe and copy the code inside the green boxes into the terminal and press Enter. There’s a pictoral guide if you’re doing the verification on Windows still, right here:
https://forums.linuxmint.com/viewtopic.php?f=42&t=291093
Let me know if you get stuck!
No problem, and again - if you experience any confusion during the process, just let me know! I also had to get help with installing Linux Mint myself when I first got started.