If you had a Darkcoin wallet you don't need to send your coins to your new Dash wallet. The only thing you need to do is install the latest version of the Dash wallet from the official website and ensure that it is using your old wallet.dat file.

If you are not sure what the previous sentences mean, please watch the tutorial for your operating system below.

https://www.youtube.com/watch?v=5V0g-qTMkpA
 

https://www.youtube.com/watch?v=nrVwcd4_2II
 

https://www.youtube.com/watch?v=0t1hFM9bNBI