How can I view the total stock of the inventory before sales ?

The On Hand quantity is the quantity you've purchased less the quantity you've sold up to the date on the report.

The Available quantity will be the same unless you use sales orders, which reduce it. Other types of transactions might impact it as well.

Changing the on hand quantity to increase it and ignore your sales won't make it more accurate. Why would you want to do that?

We want to see full flash details for the inventory in one inventory report, if changes can't be made in On Hand quantity can you please add the column of inventory in inventory report in which we can see what the inventory we have before sales.