In the case of “1M” for sfdisk, that’s “one Megabyte”… not “L Megabyte”…
Based on your last post, you are right here after “ums 0 mmc 0”
SERIAL_CONSOLE_U_BOOT
Loading Environment from MMC... OK
In: serial
Out: serial
Err: serial
Net: FEC0
Hit any key to stop autoboot: 0
=> ums 0 mmc 0
So go to here, and “copy n paste” the commands directly, don’t “try” to type them yourself…
Regards,