If you still are keeping some of your contacts to your SIM card, you can transfer and copy SIM card numbers to your phone. To import SIM contacts to LG G5, do as follows:
1. Open the Contacts app on your LG G5
2. Touch the 3-dot icon on the top right and hit the More button to view all the menu items
3. Tap to open the Manage Contacts option
4. Now you should specify where to import contacts and where to transfer and save them
5. So, in the From menu, select the SIM Card option and in the To menu, select the Phone option (You can also transfer your contacts stored in the SIM card to one of your accounts, like your Gmail account)
6. Hit the OK button
7. The list of your SIM card contacts appear, and all you have to do is either touch the Select All option or mark the contacts your want to transfer to your LG G5's memory
8. Once done, hit the Import button, read the notice and hit the Import button again.
Note that, since this process keeps the contacts both on the SIM card and Phone, there will be some duplicate contacts.