The exchange rate between the US dollar and the Nigerian naira fluctuates constantly. To determine how much a 100-dollar Amazon gift card is worth in naira, one needs to check the current exchange rate.

Typically, you can find the exchange rate through various financial institutions, online currency exchange platforms, or even at some local banks. Once you have the accurate exchange rate, you simply multiply it by 100. For example, if the exchange rate is 1 dollar = 410 naira, then a 100-dollar Amazon gift card would be worth 100 * 410 = 41,000 naira.

However, it's important to note that exchange rates are not static. They can change due to economic factors such as inflation, interest rates, and global market trends. So, it's advisable to keep an eye on the exchange rate at the time of conversion to get the most precise value of the 100-dollar Amazon gift card in naira.