Even in simplest of models I don't think it is enough info to constrain the fx rate. Even if velocity can be worked out we can't get m0.
In the simplest model all islanders are equally capable or some equilibrium arises where everyone gets the same proportions of resource. Then if resource x has $a$ units per person and total of all resources or sum of all units of the different resources is $s$ the price of each resource $x$ is simply $\frac{100a}{s}$. If the price of a resource is known in a foreign currency then one can theoretically obtain the foreign currency by selling goods in the foreign currency. In this simple theory any difference in resources would be arbitrage opportunities seeking to balance or distribute resources till they have the same abundance.
This is very simple theory. If one resource is short one place and another resource short some where's else there may be no arbitrage and thus do not cancel out.
So we assume eventually or in long run of existence of island nation, absent of any kind of trade barriers, there is no more arbitrage. Now we have $$\frac{m_a a}{s_a}=\frac{m_b b}{s_b}$$
Assuming resources eventually are evenly distributed, or even that the ratios of such resources are same, the then we see that one unit of currency equals $1_{unit \ a} =\frac{1_{unit \ b} m_b}{m_a}$.
So in this model if islanders have $m_a=100$ and u.s. have $m_b=30000$ then one island currency would be worth $\frac{30000}{100}=300$ USD.
So we see a lot of assumptions are made here. Also maybe this is too granular. Probably more needs to be considered about resource pricing. In reality there are different levels of abundance of resource and that is the primary motivating factor here.
