A third DUI in 10 years (South Carolina's "look-back period") is considered a misdemeanor in South Carolina. The specific penalties differ depending on your blood alcohol content at the time of the arrest. However, even those with a low BAC may need the help of a lawyer to try to reduce the consequences associated with a third DUI.
No matter what your BAC is at the time of your third DUI arrest in South Carolina, your driver's license will be suspended for 2 years. The only exception to this is if all 3 of your DUIs are within a 5-year period, as this results in a license suspension period of 4 years.
Either way, a month after your conviction, your car's license plate will be taken by the state, and your registration will be suspended. Once you are allowed to drive again, you will not only need to get back your plates and reinstate your registration, but you will also need to get your driver's license back. This usually requires a fee of $100, evidence of an SR22 insurance policy, and the installation of an ignition interlock device for the next 3 years. This will not allow you to start your car if your BAC is above .02 when you breathe into the device.
Additionally, you will need to complete an alcohol treatment program before you can drive again after a third DUI in South Carolina.
You have 30 days after your arrest to request a hearing in this state. If you meet this deadline, you will be able to keep your license until your court date, allowing you to drive until then. If you miss this deadline, you will not be able to drive, and since provisional licenses to get to work or school during this time are not allowed, you will be unable to get where you need to go.
State law bars you from plea bargaining down to wet reckless for your third DUI in South Carolina. Therefore, unless you find other plea options, you will likely have to either plead guilty and accept the charges, or plead not guilty. If you choose the latter, you will probably need a lawyer to help you collect evidence in your favor for when you go to court.