Default [Q] Recreate EFS partition?

Hello, I have a P5100. I had some problems with the EFS folder, and I think I made a mess.
Before I saw the mount /efs in recovery mount, now disappeared, and when I try to restore the imei with nav_data.bin does not work.
Could someone help me?
I can still see the folder / efs, but looking at the partitions I only see these:

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./adb shell mount
rootfs on / type rootfs (rw)
tmpfs on /dev type tmpfs (rw,seclabel,nosuid,relatime,mode=755)
devpts on /dev/pts type devpts (rw,seclabel,relatime,mode=600)
proc on /proc type proc (rw,relatime)
sysfs on /sys type sysfs (rw,seclabel,relatime)
selinuxfs on /sys/fs/selinux type selinuxfs (rw,relatime)
tmpfs on /tmp type tmpfs (rw,seclabel,relatime)
tmpfs on /storage type tmpfs (rw,seclabel,relatime,mode=050,gid=1028)
tmpfs on /mnt/secure type tmpfs (rw,seclabel,relatime,mode=700)
tmpfs on /mnt/fuse type tmpfs (rw,seclabel,relatime,mode=775,gid=1000)
/dev/block/platform/omap/omap_hsmmc.1/by-name/CACHE on /cache type ext4 (rw,seclabel,relatime,user_xattr,barrier=1,journal_async_commit,data=ordered,noauto_da_alloc,discard)
I can recreate it? How?
Once rebuilt, I have an old copy of the EFS folder that contain the files:

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FactoryApp
imei	
nv_data.bin
redata.bin
wv.keys
bluetooth
nv.log	
nv_data.bin.md5
wifi
Could you tell me the exact steps to take to get back the imei correct?
HELP Thank you.