Exchange 2010 - cmdlet new-mailbox issue asplaintext password

This command works if im importing from a csv file but when i try to provision a single mailbox i cant seem to get it to work unless i trigger password input.

I want to be able to automate the password entry despite it being a single mailbox being created.

This is the command

new-mailbox -Name Jackson.Pollock -Alias Jackson.Pollock -UserPrincipalName jackson.pollock@test.com -Database "Mailbox Database test1111" -OrganizationalUnit "exchange users" -RetentionPolicy 30days -PrimarySmtpAddress jackson.pollock@test.com -password (ConvertTo-SecureString Pass123456789 -AsPlainText -force) -ResetPasswordOnNextLogon $false

this is the error I keep getting

New-Mailbox : Value cannot be null.
Parameter name: parameters
At line:1 char:12

if i remove the -password command everything works normally. any ideas im stumped? ive tried 40 variations of this command.

Also this gives the same error as above

$pass =ConvertTo-SecureStringPass123456789-AsPlainText-forcenew-mailbox -NameJackson.Pollock-AliasJackson.Pollock-UserPrincipalName jackson.pollock@test.com -Database"Mailbox Database test1111"-OrganizationalUnit"exchange users"-RetentionPolicy30days-PrimarySmtpAddress jackson.pollock@test.com -password $pass -ResetPasswordOnNextLogon $false