The possessive form of the plural noun wheels is wheels'.
example: I measured the wheels' diameters and found they were different sizes.
The plural form is auto and the plural possessive is autos' (e.g. The autos' steering wheels were found to be defective.)
As it is spelled, it the plural possessive form. the singular form is toy; the plural form is toys. The singular possessive form is toy's (as in "the toy's wheels are falling off). The plural possessive form is as you spelled it - toys'. As in "All the toys' wheels and axles are falling off.
Singular possessive: secretary's Plural: secretaries Plural possessive: secretaries'
The plural is relatives. The plural possessive is relatives'.
The plural is lads. The plural possessive is lads'.
The plural form is Mexicans. The plural possessive is Mexicans'.
The plural form is suffixes. The plural possessive is suffixes'.
The plural possessive of stepsister is stepsisters'.
The plural form is echoes. The plural possessive is echoes'.
The plural form is inches. The plural possessive is inches'.
Coaster's is singular possessive. The plural is coasters, the plural possessive is coasters'.
The plural possessive is pals'.