Hi Felicia, as Soaring Eagle said, adding extensions onto your hair now will not allow the upper part of your hair to dread. The strands in each section need to move about and knot. With an extension on the end of them they would be unable to do this. So, your hair would have to dread first. By the time your hair is dreaded enough, you will have experienced what it is to grow dreads. It seems strange to write, but growing them does something to a person within their soul. By the time you put extensions on the ends, they will feel foreign to you due to what has grown within you. Sounds weird but it does happen (to most).
You could put your extensions in right now and see how you like them, but doing that won't let your hair dread, but you would have the length you want. I am not sure how long extensions last in the hair, but by the time they start to fall off, you may decide you love the look for you and can then start to grow your own. Take the Biotin in the meantime so you can get more hair growth if you go this route.
I am not sure how the Kanekalon attaches, but some types need to be crocheted in, and that is the worst thing to do for your hair as it breaks it into many pieces, so hopefully with your type you don't need to do that.
There is a small percentage of people on here who do have extensions, so if you need any tips to do it, let me know & I will find out who can help you or answer any questions about them.....remember, it's your hair and your decision....Just click on my photo in the Dreads Online box when you see I am on and a box will open so we can message live.......peace