After and on 2020/03/30 is it correct for writing grammatically?

To clear up any ambiguity, I would use this construction:

Beginning 2020/03/30, please use this template.

"Please use this template after 2020/03/30" = Do not use this template until 2020/03/31

"Please use this template as of 2020/03/30" = Start to use this template on 2020/03/30

As has been pointed out, your date format is strange (It is used mainly in Sweden and, as Yosef Baskin says, in file names.)