i want to upgrade from acrobat x to acrobat dc. is this possible?

Yes.

Go to the Adobe Products Page: https://www.adobe.com/products/catalog/software.html

Click on the Buy button next to Acrobat Pro DC, and then change the "I want to buy" option to "Upgrade" and select your current version.

Then select the other options and click on Add To Cart, and proceed to checkout.

NOTE: You'll get a full license, not a time-based subscription. If you want to switch to the subscription model (recommended) you'll need to contact Adobe directly.