Welcome to the community!
Are you able to get wired internet at your residence? If home internet is available at your home, that might be a better option for poor cellular signal internet.
Assuming home internet is not an option, do you get good cellular signal outside? If your area has generally poor signal, an external modem might still be ineffective. If you do get some signal, you might consider getting a signal booster which might be able to amplify signal enough for adequate internet access. Any modem or signal booster would need to have compatible bands/frequencies. You can view the compatible bands/frequencies here.
Hope this helps 😀