Typically bonds are quoted in a percentage out of 100%. Assuming a face value of USD 1,000, a quantity of 1 and a price of 97.55, the value of the trade will be 1000 x (97.55 x 0.01) = 975.5. You would then multiply that value by 1,000 to get to a market value of USD 1 MM. An easy way to do this in TWS is as follows:
The face value of a hypothetical bond is USD 1,000 and the price is 97.65. If you wish to buy 1,000,000 (975,650) USD of the bond, add the bond to a blank line on your watchlist, right click on the line and select Trade followed by Order Entry. Next, change the quantity to $1,000k. If you preview the order you will now see a market value of 975,650 USD.