Grids run at a fixed frequency. The UK, Europe, the UAE, Qatar, Oman, India and most of Africa and Asia use 50 Hz. The US, Canada, most of Latin America, Saudi Arabia, South Korea and Taiwan use 60 Hz.
A generator’s frequency is set by its speed and number of poles: Hz = rpm × poles ÷ 120. The Wärtsilä 34SG runs at 750 rpm with 8 poles for 50 Hz, and at 720 rpm with 10 poles for 60 Hz. Same engine family, different machine.
Converting a unit usually means a new generator, often a new gearbox for turbines, and retesting. Once costed, a different unit is usually cheaper.
What to ask first: the site’s frequency and whether the plant is grid-connected or in island mode. Then check site rating. Price comes third.