How can I change my Windows 10 32 bit to 64-bit without formatting?

After you have installed Rufus:

1. Launch it.
2. Select ISO Image.
3. Point to the Windows 10 ISO file.
4. Check off Create a bootable disk using.
5. Select GPT partitioning for EUFI firmware as the Partition scheme.
6. Choose FAT32 NOT NTFS as the File system.
7. Make sure your USB thumbdrive in the Device list box.
8. Click Start.