Where are pre-market or after-hours quotes displayed?

Just look at the Bid and Ask price

Stocks naturally move up or down during the regular trading session. However, the same can occur before the market opens, as well as after the market closes. Although the Last price or the Change in price of a stock or ETF does not change during the extended market session, you can see any price action by looking at the Bid and Ask price. Below are examples of SPY closing at $289.05, but due to pre-market action, you'll see that the bid and ask have deviated from the closing price.

Desktop Platform

Web Browser Platform

Mobile Platform

You can view the bid and ask price by tapping the symbol in a watchlist to view quote details. Additionally, you can also view the bid and ask by entering the symbol in the Trade tab and viewing the quote details in Stock Mode.