Will this laptop run these games and if so how well?

Lenovo B50-30 15.6-Inch Laptop (Intel Celeron N2840 2.16Ghz Processor, 4 GB RAM, 500GB HDD, Windows 8.1, HDMI Webcam Bluetooth USB3)

Games: black ops 2, modern warfare 2 and Skyrim.

No.
Reason being:
Intel Celeron is Intel's worst processor next to the Atom. Very under performing and if you research a Celeron, they score the worst in benchmarks.
4GB of RAM is not great either. Most gaming computers will have a minimum of 8.
Also, no dedicated GPU… You are probably running Intel HD 4000 or 5000 graphics which SUCK for gaming.

There's no way to upgrade a laptop unfortunately with the exception of RAM (but even a RAM upgrade won't help you)