Personally I recommend returning the battery and obtaining the correct one.

If you are insistent on doing this. I am counting 9 wires, not 8. The connector is a 9-pin type, 3 for ground, 3 for V+, SMC+ and SMC-, and one for system sense (center pin). The wires must be soldered together and the connections protected by heat shrink tubes. This will take away from their flexibility and may cause them not to sit correctly for the case to close properly. If you don't solder the wires and protect the connections with heat shrink tubes that may cause other problems.

The typical MBP battery connector pinout is:

1 +12V

2 +12V

3 +12V

4 SMBUS_SMC_BSA_SCL

5 SYS_DETECT_L

6 SMBUS_SMC_BSA_SDA

7 GND

8 GND

9 GND

Within reason I have given the information you requested. Batteries don't just die. Your battery is a little over a year old and should have plenty of life. It seems to me that this laptop may have other problems that cause you to believe your battery is dead. Did you confirm battery health with Coconut Battery or iStat? Has this laptop experienced liquid damage? Please tell us more about why you believe the battery is dead.