one shot mode pwm

You can enable an interrupt on the falling edge of your timer and count how often you had a falling edge and when you got the wanted number of pulses you can disable and reset the timer module.

Don't know if there is a complete code sample available but you should be able to get it after you understood some of the general timer code examples.

There is no 'one-shot' operation, The timer is either running (cyclic), or stopped. However, as Bernhard suggested, you can let it trigger an interrupt on the end of a cycle (TACTLs TAIE bit, or TACCTL0s CCIE bit) and disable the timer.
There are ways to generate a one-shot pulse, e.g. configuring an SPI output with a baudrate so that n '0' bits have the required low-pulse length, but this is more advanced stuff.