Hi @YOUNGDONGLEE8988,
You can't really. Assuming this was the volumetric attack, by the time malicious traffic reached your device, your uplink was already filled. Your upstream provider should protect you from DDoS attack, or you need to go for dedicated DDoS solution.
Best thing you can do on your devices is to keep up to date software on them, which are fixing known security issues, so you won't get affected with non-volumetric attacks.
BR,
Milos