Use this latest png file: File:Wikipedia-logo-pa-celebration.png

Please do this task so that the logo changes right at the moment we reach 20,000.

That cannot be guaranteed. Where is the current count of articles?

You can check this on the main page. We have 19,917 articles as of now.

https://pa.wikipedia.org/wiki/%E0%A8%AE%E0%A9%81%E0%A9%B1%E0%A8%96_%E0%A8%B8%E0%A8%AB%E0%A8%BC%E0%A8%BE

It there any way i can do this on our local wiki ?

Yes, you can add CSS to common.css to change the logo on most pages (but not sensitive things such as login pages, preferences, etc.)

I have tried this and failed. We have reached 19,922 articles. Please make sure this happens at the right time.

In T120368#1855441, @satdeep_gill wrote:

Please make sure this happens at the right time.

Please read T120368#1853678 again.

I asked a commons admin to protect the file there, which has been done.
We (either a local admin or a global interface editor like me) will need to add something like .mw-wiki-logo { background-image: url(https://upload.wikimedia.org/wikipedia/commons/a/a8/Wikipedia-logo-pa-20%2C000_articles-latest_v2.svg); } to MediaWiki:Common.css when it's time.