Capital gain tax on asset purchased prior to 2000-01

Get valuation certificate of the house property as on 01.04.2001, from a registered valuer.

Based on that the indexed cost can be calculated, as base rate has changed to 100 for FY 2001-02 & same is 280 for FY 2018-19.

you need to arrive at the market value of the property as on 01.04.2001 probably from a valuation officer.
if the value so arrived us higher than the cost mentioned as on dec93 then you need to take the market value and this needs to be indexed and deducted from the sale consideration of 30lacs.balance us taxable as capital gains. if you have paid any brokerage or commission to the agent the same us also deductible.
you can either invest the capital gains in a residential property or in capital gains bonds max upto 50 lacs. if you invest in bonds after 31.03.19 then the lock in period is 5years else 3years

u can also take the value from the municipal survey rate as of year 2000-01 if it's available. but registered valuers certificate is preferable.