if yesterday the stock prices high price is 354 & ...

If you’re comparing which price is better to sell at, the higher price is better:

• Yesterday’s high = 354
• Today’s high = 345
• Best (higher) sell value = 354

But if you’re asking what’s the best value you can sell at today, you can only sell at today’s available prices—so the best-case today would be 345 (if you could actually get filled at the day’s high).

If you want to try for a specific price today, you’d typically use a limit sell order at your target (just know it may not fill if the price never reaches it).