How to plug Arduino Micro on Chromebook?

Hello,
I plugged an Arduino Micro on a Chromebook, but I don’t know where it is mounted. I got these info:

$ ls -l /dev/ttyACM*
ls: cannot access '/dev/ttyACM*': No such file or directory
$ ls /dev/sda* 
ls: cannot access '/dev/sda*': No such file or directory
$ df
Filesystem     1K-blocks     Used Available Use% Mounted on
/dev/vdb        42636824 12803940  28336524  32% /
none                 492        0       492   0% /dev
devtmpfs         1420720        0   1420720   0% /dev/tty
/dev/vdb        42636824 12803940  28336524  32% /dev/kvm
tmpfs                100        0       100   0% /dev/lxd
tmpfs                100        0       100   0% /dev/.lxd-mounts
run              1423104       28   1423076   1% /dev/.host_ip
/dev/root         170360   168192         0 100% /dev/.ssh/sshd_config
9p               1948588     1092   1947496   1% /mnt/chromeos
/dev/vda           48384    48320         0 100% /opt/google/cros-containers
tmpfs            1423104     7928   1415176   1% /dev/shm
tmpfs            1423104   106716   1316388   8% /run
tmpfs               5120        0      5120   0% /run/lock
tmpfs            1423104        0   1423104   0% /sys/fs/cgroup
tmpfs             284620       72    284548   1% /run/user/1000
$ sudo fdisk -l
$ lsblk
NAME  MAJ:MIN RM  SIZE RO TYPE MOUNTPOINT
vda   254:0    0   48M  1 disk /opt/google/cros-containers
vdb   254:16   0 40.7G  0 disk /dev/bus/usb/002/001
pmem0 259:0    0  170M  0 disk /dev/.ssh/sshd_config

On Chrome OS it is not possible to run Arduino IDE, so I am using Platformio on Atom. When I try to upload a sketch I get:

Flash: [=         ]  12.6% (used 3620 bytes from 28672 bytes)
Configuring upload protocol...
AVAILABLE: avr109
CURRENT: upload_protocol = avr109
Looking for upload port...
Error: Please specify `upload_port` for environment or use global `--upload-port` option.
For some development platforms it can be a USB flash drive (i.e. /media/<user>/<device name>)
*** [upload] Explicit exit, status 1
========================== [FAILED] Took 3.92 seconds ==========================

What shall I do?
Thank you

I don’t have a chrome book, so I can say for sure, but dmesg | tail on most Linux distros will tell you what port a device was assigned to. Make sure you run the command immediately after plugging the device into a USB port. Otherwise the messages may get lost in the noise.

dmesg | tail
[(DELETED)
[843343.367372] usb 10-1.2: new full-speed USB device number 6 using xhci_hcd
[843343.482663] usb 10-1.2: New USB device found, idVendor=1a86, idProduct=7523
[843343.482667] usb 10-1.2: New USB device strings: Mfr=0, Product=2, SerialNumber=0
[843343.482669] usb 10-1.2: Product: USB2.0-Serial
[843343.484355] ch341 10-1.2:1.0: ch341-uart converter detected
[843343.485576] usb 10-1.2: ch341-uart converter now attached to ttyUSB0

Ignore the first part of that ouput It has nothing to do with the ttyUSB0 port connection. I deleted it.
If dmesg doesn’t work, take a look at /var/log/messages after you plug the device in. It may contain similar messages to what dmesg gave me.