If i take pachkhan even for single day thecan i get punya and how much

Yes. In Jain Dharma, even taking pachkhan for one day can give punya if it is taken with true intention, self-restraint, and proper observance.

But how much punya cannot be measured exactly in words. In Jain teaching, the result depends on:

• Bhavna: the inner intention
• Shuddhi: purity of mind and conduct
• Niyam-palan: how well you follow the vow
• Degree of restraint: the level of renunciation you practice

So:

• A sincere one-day pachkhan gives good punya
• A longer and more careful observance gives greater punya
• If pachkhan is taken only formally, with little seriousness, the benefit is less

In Jain view, pachkhan is not only for earning punya, but mainly for reducing sins, practicing control, and moving toward the path of liberation.

So the short answer is: Yes, you do get punya even for a single day, but the amount depends on your sincerity and observance, and it cannot be precisely counted.

If you want, I can also explain the difference between punya from pachkhan and punya from tapa in simple Jain terms.