All flights to Portugal leave from Chișinău airport, with only one direct flight per week, although a lot of alternative with a single stopover are available. Prices range from €45 to €240.
A complete itinerary for traveling from Moldova to Portugal was compiled by the amazing guys at the travel website DeFérias (https://www.deferias.pt/) for which we are very thankful! You can find it in the following PDF:
DeFerias - From Moldova to Portugal.pdf