To see up to seven days of trades, use the Trade Log, accessible from the New Window drop-down in Mosaic and the Account menu in Classic TWS. In Mosaic, you can also see today's trades in the Trades tab of the Activity tile.
Trade information such as commissions and fill prices are reflected in the table. You can find out more about the Trade Log in the TWS Users' Guide.
Trades older than seven days can be found in your Activity Statements. See Where can I find my transaction or trade history?