My Answer was:
Dear Engineer Abrar Haware,
Thank you for your email. A Tender Program is being created with very limited information. Accordingly, estimating accurate manpower is a challenging task. Therefore, I usually communicate with the estimation team to get from them how many manhours they calculated for their cost estimation and distribute it accordingly to project activities. Alternatively, I make a rough estimate of the manhours based on similar previous projects and consider the built-up area in my calculations as follows:
1- Project A with a built-up area of 1,000 sqm has 20,000 manhours.
2- Tender project of a similar type with a built-up area of 500 sqm, the roughly estimated manhours are 10,000.