Question

if point of suspension of pendulum is having a acceleration a w.r.t. to ground, at an angle with horizontal then the time period is

Answer 1

Well it depends on the context of your question. If you're being introduced to General Relativity, then you're just going to assume, in the spirit of the equivalence principle, that gravity and the acceleration cannot be told apart from the pendulum's standpoint, so the acceleration is obviously $a+g$.

If you need to do it from first principles in a Newtonian setting, draw a free body diagram of the bob. First, let's do the unaccelerated pendulum.