[RussEfarmer]

There's no special tricks behind converting the steamids we see in game from that type to steamid64 and steamid3 (the kind you see in CSGO), it's all just math. Math so easy that you can actually do it on your calculator:

Convert steamid to steamid3 profile link:
Let X, Y and Z equal these components of the steamid: STEAM_X:Y:Z
Use the formula W=Z*2+Y and convert to this link:
https://steamcommunity.com/profiles/[U:1:W]

And it's that easy. Multiply the last part by 2, add the middle to it, slam it on the end of that link, and you have a profile URL.

You can actually convert steamids to steamid64, but the numbers are a little bigger:
Let X, Y and Z equal these components of the steamid: STEAM_X:Y:Z
Let V equal the account identifier for normal user accounts: 76561197960265728
Use the formula W=Z*2+V+Y and convert to this link:
https://steamcommunity.com/profiles/W