The physical space that 1 billion dollars in 100 dollar bills would take up depends on several factors, including the weight and size of the bills themselves, the method of storage, and the currency exchange rate. In this answer, we will explore each of these factors and estimate the amount of space that 1 billion dollars in 100 bills would occupy.

Firstly, let’s look at the weight and size of the bills. The weight of a single 100 dollar bill is approximately 1 gram, and the dimensions are 155.956 x 66.294 mm. Therefore, 1 million dollars in 100 dollar bills would weigh approximately 10 kilograms (22.046 pounds) and measure approximately 155.956 x 662.94 x 76.2 millimeters (6.14 x 2.61 x 0.3 inches). Multiplying this by 1,000 gives us the weight and size of 1 billion dollars in 100 bills, which would be 10,000 kilograms (22,046 pounds) and 155.956 x 662.94 x 762 millimeters (6.14 x 2.61 x 30 inches).
Secondly, let’s consider the method of storage. If we assume that the bills are stacked neatly and securely, without any gaps or air pockets, we can estimate the volume of the stack using the formula for the volume of a rectangular prism: V = l x w x h. Using the dimensions calculated above, the volume of 1 billion dollars in 100 bills would be approximately 77,062,301 cubic millimeters (4,707 cubic inches) or 77.06 cubic meters (2,722 cubic feet).
However, it is important to note that this calculation assumes that the bills are perfectly flat and compact. In reality, bills are not perfectly flat and contain small creases, which can cause them to take up slightly more space. Additionally, it is unlikely that all of the bills would fit perfectly into a single stack, and multiple stacks would need to be used to store 1 billion dollars. This would require additional space for the edges of the stacks, as well as some space between the stacks to allow for easy access.
Thirdly, let’s consider the currency exchange rate. The exchange rate between the US dollar and other currencies can fluctuate over time, which can affect the value of 1 billion dollars in terms of other currencies. For example, if we convert 1 billion US dollars to euros at an exchange rate of 1 USD = 0.83 EUR, then 1 billion dollars would be equivalent to approximately 830 million euros. The physical space required to store 830 million euros in 100 euro bills would be slightly different from the space required to store 1 billion US dollars in 100 dollar bills, as the weight and dimensions of the bills are different.
In conclusion, the physical space that 1 billion dollars in 100 dollar bills would take up depends on several factors, including the weight and size of the bills, the method of storage, and the currency exchange rate. Based on the calculations above, 1 billion dollars in 100 bills would weigh approximately 10,000 kilograms (22,046 pounds) and measure approximately 155.956 x 662.94 x 762 millimeters (6.14 x 2.61 x 30 inches). However, it is important to note that these calculations are rough estimates, and the actual amount of space required to store 1 billion dollars in 100 bills may vary depending on the specific circumstances.