You have to get details from central government revenue department check allotment of land as well in state revenue department. 

You can get maximum records from home minister of central government.

You will get the land documents in the local settlement office in nainital.

It can be enquired from Land and Development Office.

Sir, contact number cannot be provided here as advocates are not allowed to solicit clients in India. 

You'll have to book a consultation from this website.

Check the records of tehsildar / collector office , chief settlement commissioner in state where land were allotted

You can obtain contact details from the website 

- The displaced persons from Pakistan were allotted lands in lieu of the land left by them in Pakistan during the period of 1950 .

- You can get the details of allotted lands from the Official Website of Department Revenue,Rehabilitation and Disaster Management, Government of Punjab,India .

- You can also lodge your complaint for the said purpose , through this webstie as well.

The particulars of these documents could be available at chief settlement commissioner office. 

For the land you should have the name of the villages and tehsil district etc. Land records can be obtained and ownership determined on that basis. Then you can obtain duplicate copies of the documents.

Regards 

The particulars of required information can be get from the office of chief settlement commissioner of concerned area i.e nainital.

An extensive search will have to be conducted in the office of jurisdictional sub-registrar. Engage a local lawyer.

It's  a registered land will have record in the department. If not you need to approach court

You have to lodge FIR for loss of original  documents.

Give advertisment in two news papers for loss of original documents.

After that make an affidavit of loss of original documents in that affidavit mention about FiR and news paper advertisment attach copy of news papers and FIR.

And apply for true copy of document in sub registrar office by attaching affidavit with application.

If the allottee is alive then he can approach the land revenue department at Nainital with his identity card or any other details, or his legal heirs can approach the authority concerned with all the details in their possession.

Inquire about the same  and comply with the requirements they may be asking you to comply.

There are chances that you get some idea about it, because it is more than 7 decades that you have never bothered about it, hence you may have to strain a little more to get the details, sometimes you may not get any details at all.