Hickel and colleagues find that, in 2021, the economies of the global North net-appropriated 826 billion hours of embodied labour from the global South, across all skill levels and sectors. Unequal exchange is understood to be driven in part by systematic wage inequalities. They find Southern wages are 87-95% lower than Northern wages for work of equal skill. While Southern workers contribute 90% of the labour that powers the world economy, they receive only 21% of global income.
I've updated my first response.
But as for looking at it in a Marxist way (obviously you are correct in that Marx did not mention unequal exchange, the chapter of Capital based on international trade never saw daylight and it is impossible to know what Marx would've written), Samir Amin came up with two accumulation models.