I bought Skyrim a time ago, but only the main game. I do not see the DLCs to buy anymore. Do I have them?
I went to the link mentioned here, but it doesn't show the DLCs.
The DLCs as well as the original base game have been hidden, but are still accessible. This happens with other games as well when a remastered version is released.
If you had previously owned Skyrim: Dragonborn through steam, you would have automatically received the Skyrim: Special Edition, which is the remastered, all encompassing version of the game, at no additional cost when it was released. Once that version was released, they hid the original from the store.
Thankfully, I still have the base game in my library and was able to pull up the direct link to the DLC purchase page as well as a free texture upgrade patch. You can find those here and if you already own one of the DLC packages, it will say "already in library". The base game is located here.
Give it some thought thought: Special Edition runs $40 whereas the DLC packages for the original version cost $45 ($40 of that is between Dawnguard and Dragonborn).